The largest immigration boom from a single country to the United States is over, according to a recent report from the Pew Hispanic Center. For the first time since the Great Depression, more Mexicans are leaving the United States than arriving, ending a decades-long wave that brought 12 million Mexican immigrants into the U.S. — more than half of whom entered illegally.

Immigration is a major political issue, especially in a campaign where both parties are vying for the Latino vote, which as TIME predicted could determine the outcome of the 2012 election.

According to the report, the standstill in immigrants coming to the U.S. can be attributed to:

Weakened U.S. job and housing construction markets.

Heightened border enforcement.

A rise in deportations.

The growing dangers associated with illegal border crossings.

The long-term decline in Mexico’s birth rate.

Changing economic conditions in Mexico.

As Jeffrey Passel, a senior demographer at Pew and co-author of the report, told the Washington Post, “The diminished flow appears largely to be a drop in unauthorized immigrants.” The decrease could be attributed to fears of border control and deportation, two areas of immigration control that have significantly intensified efforts to keep unauthorized immigrants out of the country.

And the efforts have had results. In 2005, according to the report, more than 1 million immigrations tried to cross the border illegally. By 2011, that number dropped to 286,000.

Deportations have similarly reached record numbers, with roughly 400,000 illegal immigrants being deported in 2010, 73 percent of them Mexicans.

For years, many immigrants accepted hostility from native-born Americans as a condition of access to the opportunities available in the United States. However, the loss of working-class jobs, particularly in construction, has led more and more to reconsider the tradeoffs. Now, just as many Mexican immigrants are returning to Mexico from the U.S. as are arriving in the states — if not more.

Whether the Pew report will have implications on immigration policy remains to be seen, especially given how both countries’ precarious economic health could greatly affect the flow of immigrants. “It gives us the space to figure out how do we fix the legal immigration system so when the economy bounces back, how do we respond?,” said Clarissa Martinez, director of immigration and civic engagement at the National Council of La Raza, a Latino advocacy group, to the Washington Post. Meanwhile, the next immigration battle is shaping up fast: on Wednesday, the U.S. Supreme Court hears arguments concerning a controversial Arizona law that allows local and state police to stop and check people they suspect of being illegal immigrants.